[BUG] Bad output indices from `pointcloud_search()` with batched shading

**Describe the bug**

When using `pointcloud_search()` with batched shader execution, the output `indices` array is not being filled correctly. It looks a little like OSL thinks the output is a uniform rather than a varying value, but I don't know enough about what is going on under the hood to be sure.

**OSL version and dependencies**

* OSL branch/version: 1.14.5.1
* OS: Rocky 8.8
* C++ compiler: GCC 11.2.1
* LLVM version: 15.0.7
* OIIO version: 3.0.6.1

**To Reproduce**

Steps to reproduce the behavior:

1. `oslc search.osl` (source code in section below).
2. `testshade -g 16 16 -batched -param file cloud.geo search.oso -o Cout batched.png`
3. `testshade -g 16 16 -param file cloud.geo search.oso -o Cout unbatched.png`
4. Compare `batched.png` to `unbatched.png`. The latter has the expected results, and the former does not.

In the above commands, `cloud.geo` is `testsuite/pointcloud-fold/cloud.geo` from the OSL repo.

**Evidence**

search.osl

```
shader search( string file = "", output color Cout = 0 )
{
int indices[1];

// Uncommenting this workaround gives the expected results in batched
// mode. I suspect it works by tricking OSL into realising that `indices`
// is a varying quantity.
// indices[0] = P[0];

if( pointcloud_search( file, P, 1, 1, "index", indices ) )
{
Cout = color( indices[0] / 15.0 );
}
else
{
Cout = color( 1, 0, 0 );
}
}
```

batched.png :

unbatched.png :

Ejecuta los comandos oslc y testshade indicados usando testsuite/pointcloud-fold/cloud.geo y compara después la salida por lotes con la salida sin lotes. Empieza en el punto de entrada pointcloud_search y sigue cómo se gestiona el array de índices de salida durante la ejecución por lotes. Se considera terminado cuando batched.png coincide con los resultados esperados de la ejecución sin lotes sin el workaround.

Escrito por el modelo de indexación a partir del texto del issue.